An opening means which quickly drives an operating shaft of a vacuum valve toward an opening direction by electromagnetic repulsion comprises an electromagnetic repulsion coil and a ring copper plate located opposite to it where the vacuum valve is opened by quickly exciting the electromagnetic repulsion coil of the opening means by a capacitor discharge or the like and using an electromagnetic repulsive force such as eddy current which occurs in the coil current and copper plate.
Circuit breakers with an electromagnetic repulsion mechanism are classified into direct-current circuit breakers and high-speed circuit breakers. In the former type, charge in a previously charged capacitor is injected in a direction reverse to the direction of line current to make a zero current point forcedly to interrupt the current. If an accidental short circuit occurs in the DC line, an overcurrent as determined by resistance and inductance as circuit constants, like fast-rising short-circuit current, flows, necessitating the breaker to operate quickly.
On the other hand, a high speed breaker is used in a private power generation system or the like and introduced in order to prevent electrical leakage from the private power generation equipment in a power failure, to prevent power supply systems from going down due to an overload, or assure continuous operation of a critical load by quickly switching from a defective power system to a normal one. This type of breaker also uses an electromagnetic repulsion mechanism because a response of the breaker must be within several milliseconds after receipt of an opening command.
One known example of such a breaker with an electromagnetic repulsion driving mechanism is the one disclosed in JP-A No. 2000-299041 which includes a vacuum valve, an operating mechanism provided in the opening and closing of the vacuum valve, and an electromagnetic repulsion driving mechanism provided midway in the operating mechanism and further includes a mechanism for reducing rebound of the movable electrode shaft in the course of current interruption.